The invention relates to aeroengines fitted with a variable section nozzle, and more particularly to the connection that enables actuating movements to be transmitted to each flap.
Document U.S. Pat. No. 7,533,533 describes a variable section nozzle having a plurality of internal flaps or “hot flaps” channeling the primary or main air stream of the engine. The internal flaps are actuated by control levers so as to modify the profile of the primary stream from the turbine engine (i.e. the ejection section(s) depending on whether the nozzle is merely a converging nozzle or a converging and diverging nozzle).
In Document U.S. Pat. No. 7,533,533, only every other internal flap is controlled directly by an actuator that is connected to the control lever of the flaps. The flap adjacent to the flap fitted with an actuator is drivingly coupled by connection clevises that transmit a fraction of the force produced by the actuator to the coupled flap.
Although that solution enables the variable section nozzle to be made lighter in weight by minimizing the number of actuators in the nozzle, it leads to asymmetry in the mechanical loading of the nozzle. The levels of mechanical forces and the directions of those forces on the portions of the flap control levers fastened to the ejection casing of the nozzle differ depending on whether the levers are or are not fitted with an actuator. The levers without actuators are controlled in a manner that is less rigid than the control of the levers with actuators, which leads to an offset in the angular position for the coupled flaps. For this purpose, it is necessary to perform pre-loading on the coupled flaps in order to compensate for this offset.
This mechanical unbalance leads to a high level of static indeterminacy in the nozzle, to a linkage that is loaded tangentially, and to a high level of wear of the moving parts of the lever control devices.
Consequently, there exists a need to enable mechanical forces to be transmitted in balanced and synchronized manner to each flap of the nozzle, without significantly increasing the overall weight of the nozzle.